Tool bit

ABSTRACT

A tool bit includes a hexagonal drive portion, a working end, and a shank interconnecting the drive portion and the working end. The shank includes an outer peripheral surface having a curvature in a plane including a central axis of the tool bit. The outer peripheral surface having the curvature includes a length in the direction of the central axis. A ratio of the length of the outer peripheral surface having the curvature to the length of the tool bit is between about 0.2:1 and about 0.7:1.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 13/759,171 filed on Feb. 5, 2013, which is a continuation ofU.S. patent application Ser. No. 12/669,200 filed on Jan. 15, 2010, nowU.S. Pat. No. 8,418,587, which is a national phase application under 35U.S.C. §371 of International Patent Application No. PCT/US2009/063515filed on Nov. 6, 2009, which claims priority to U.S. Provisional PatentApplication No. 61/112,318 filed on Nov. 7, 2008, the contents of all ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to tool bits, and more particularly totool bits configured for interchangeable use with a driver.

BACKGROUND OF THE INVENTION

Tool bits, or insert bits, are often used with drivers configured tointerchangeably receive the bits. For example, typical insert bits eachinclude a hexagonal drive portion, a head or tip configured to engage afastener, and a cylindrical shank connecting the drive portion and thetip. Drivers include a socket having a hexagonal recess in which thehexagonal drive portion of an insert bit is received and a stem or shankextending from the socket, which can be coupled to a handle for hand-useby an operator, or a power tool (e.g., a drill) for powered use by theoperator. An interference fit between the hexagonal drive portion of theinsert bit and the socket may be used to axially secure the insert bitto the driver, or quick-release structure may be employed to axiallysecure the insert bit to the driver.

SUMMARY OF THE INVENTION

The invention provides, in one aspect, a tool bit including a hexagonaldrive portion, a working end, and a shank interconnecting the driveportion and the working end. The shank includes an outer peripheralsurface having a curvature in a plane including a central axis of thetool bit. The outer peripheral surface having the curvature includes alength in the direction of the central axis. A ratio of the length ofthe outer peripheral surface having the curvature to the length of thetool bit is between about 0.2:1 and about 0.7:1.

Other features and aspects of the invention will become apparent byconsideration of the following detailed description and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a tool bit according to one constructionof the invention.

FIG. 2 is a side view of the tool bit of FIG. 1.

FIG. 3 is a top view of the tool bit of FIG. 1.

FIG. 4 is a front view of the tool bit of FIG. 1.

FIG. 5 is a rear view of the tool bit of FIG. 1.

FIG. 6 is exploded perspective view of the tool bit of FIG. 1.

FIG. 7 is a perspective view of a tool bit according to anotherconstruction of the invention.

FIG. 8 is a side view of the tool bit of FIG. 7.

FIG. 9 is a top view of the tool bit of FIG. 7.

FIG. 10 is a front view of the tool bit of FIG. 7.

FIG. 11 is a rear view of the tool bit of FIG. 7.

FIG. 12 is a perspective view of a tool bit according to anotherconstruction of the invention.

FIG. 13 is a side view of the tool bit of FIG. 12.

FIG. 14 is a top view of the tool bit of FIG. 12.

FIG. 15 is a front view of the tool bit of FIG. 12.

FIG. 16 is a rear view of the tool bit of FIG. 12.

FIG. 17 is exploded perspective view of a tool bit according to yetanother construction of the invention.

FIG. 18 is an assembled side view of the tool bit of FIG. 17.

FIG. 19 is a perspective view of a tool bit according to oneconstruction of the invention.

FIG. 20 is a side view of the tool bit of FIG. 19.

FIG. 21 is a front view of the tool bit of FIG. 19.

FIG. 22 is a rear view of the tool bit of FIG. 19.

FIG. 23 is a perspective view of a tool bit according to anotherconstruction of the invention.

FIG. 24 is a side view of the tool bit of FIG. 23.

FIG. 25 is a front view of the tool bit of FIG. 23.

FIG. 26 is a rear view of the tool bit of FIG. 23.

FIG. 27 is a perspective view of a tool bit according to anotherconstruction of the invention.

FIG. 28 is a side view of the tool bit of FIG. 27.

FIG. 29 is a front view of the tool bit of FIG. 27.

FIG. 30 is a rear view of the tool bit of FIG. 27.

FIG. 31 is a perspective view of a tool bit according to yet anotherconstruction of the invention.

FIG. 32 is a side view of the tool bit of FIG. 31.

FIG. 33 is a front view of the tool bit of FIG. 31.

FIG. 34 is a rear view of the tool bit of FIG. 31.

FIG. 35 is a perspective view of a tool bit according to yet anotherconstruction of the invention.

FIG. 36 is a side view of the tool bit of FIG. 35.

FIG. 37 is a front view of the tool bit of FIG. 35.

FIG. 38 is a rear view of the tool bit of FIG. 35.

FIG. 39 is a perspective view of a tool bit according to oneconstruction of the invention.

FIG. 40 is a side view of the tool bit of FIG. 39.

FIG. 41 is a front view of the tool bit of FIG. 39.

FIG. 42 is a rear view of the tool bit of FIG. 39.

FIG. 43 is a perspective view of a tool bit according to anotherconstruction of the invention.

FIG. 44 is a side view of the tool bit of FIG. 43.

FIG. 45 is a front view of the tool bit of FIG. 43.

FIG. 46 is a rear view of the tool bit of FIG. 43.

FIG. 47 is a perspective view of a tool bit according to anotherconstruction of the invention.

FIG. 48 is a side view of the tool bit of FIG. 47.

FIG. 49 is a front view of the tool bit of FIG. 47.

FIG. 50 is a rear view of the tool bit of FIG. 47.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting.

DETAILED DESCRIPTION

FIGS. 1-6 illustrate a tool bit or an insert bit 10 including ahexagonal drive portion 14, a head or tip 18 configured to engage afastener, and a shank 22 interconnecting the drive portion 14 and thetip 18. The hexagonal drive portion 14 is intended to be engaged by anyof a number of different tools, adapters, or components to receivetorque from the tool, adapter, or component to rotate the insert bit 10.For example, the insert bit 10 may be utilized with a driver including asocket (not shown) having a corresponding hexagonal recess in which thehexagonal drive portion 14 of the insert bit 10 is received. The drivermay also include a stem extending from the socket, which may be coupledto a handle for hand-use by an operator or to a chuck of a power tool(e.g., a drill) for powered use by the operator. An interference fitbetween the hexagonal drive portion 14 of the insert bit 10 and thesocket may be used to axially secure the insert bit 10 to the driver.Alternatively, a quick-release structure may be employed to axiallysecure the insert bit 10 to the driver. With reference to FIGS. 1-3, thedrive portion 14 of the insert bit 10 includes a groove 26 into whichthe quick-release structure (e.g., a ball detent) may be positioned toaxially secure the insert bit 10 to the driver. Alternatively, thegroove 26 may be omitted from the drive portion 14 of the insert bit 10should an interference fit between the socket and the drive portion 14be employed.

With continued reference to FIGS. 1-3, the tip 18 of the insert bit 10is configured as a Philips-style tip 18 (see also FIG. 4).Alternatively, the tip 18 of the insert bit 10 may be differentlyconfigured to engage different style fasteners. For example, the tip 18of the insert bit 10 may be configured as a straight blade (otherwiseknown as a “regular head”) to engage fasteners having a correspondingstraight slot. Other tip configurations (e.g., hexagonal, star, square,etc.) may also be employed with the insert bit 10.

With reference to FIGS. 1-3, a portion 30 of the shank 22 is concave,including opposite end portions 34 and a reduced diameter mid-portion38. Specifically, the concave portion 30 of the shank 22 includes anouter peripheral surface 42 having a curvature in a plane including acentral axis 46 of the insert bit 10 (i.e., in a plane parallel to theplane of the page of FIGS. 2 and 3). In a configuration of the insertbit 10 having an overall length Lt of about 1 inch, the curvature isdefined by a radius R of about 0.15 inches to about 0.75 inches.Alternatively, in a configuration of the insert bit 10 having an overalllength Lt of about 2 inches, the curvature is defined by a radius R ofabout 0.85 inches to about 2.75 inches. Further, in a configuration ofthe insert bit 10 having an overall length Lt of about 3 inches, thecurvature is defined by a radius R of about 7 inches to about 15 inches.

With continued reference to FIGS. 1-3, in a configuration of the insertbit 10 having an overall length Lt of about 1 inch, the length L of theconcave portion 30 of the shank 22 is about 0.2 inches to about 0.35inches (i.e., the ratio of L/Lt is about 0.2:1 to about 0.35:1).Alternatively, in a configuration of the insert bit 10 having an overalllength Lt of about 2 inches, the length L of the concave portion 30 ofthe shank 22 is about 0.5 inches to about 0.7 inches (i.e., the ratio ofL/Lt is about 0.25:1 to about 0.35:1). Further, in a configuration ofthe insert bit 10 having an overall length Lt of about 3 inches, thelength L of the concave portion 30 of the shank 22 is about 1.5 inchesto about 1.8 inches (i.e., the ratio of L/Lt is about 0.5:1 to about0.6:1).

With continued reference to FIGS. 1-3, in a configuration of the insertbit 10 having an overall length Lt of about 1 inch, a ratio of theradius R to the length L is equal to about 0.43:1 to about 3.75:1.Alternatively, in a configuration of the insert bit 10 having an overalllength Lt of about 2 inches, a ratio of the radius R to the length L isequal to about 1.21:1 to about 5.5:1. Further, in a configuration of theinsert bit 10 having an overall length Lt of about 3 inches, a ratio ofthe radius R to the length L is equal to about 4.12:1 to about 10:1. Inthe illustrated construction of the insert bit 10, which is configuredhaving an overall length Lt of about 2 inches, the length L of theconcave portion 30 of the shank 22 is about 0.514 inches, and the radiusR of the concave portion 30 of the shank 22 is about 1.149 inches. Assuch, the ratio of the radius R to the length L is about 2.24:1. Also,in the illustrated construction of the insert bit 10, the diameter D1 ofthe mid-portion 38 is about 71% of the diameter D2 of each of the endportions 34. Alternatively, the diameter D1 of the mid-portion 38 may beabout 60% to about 80% of the diameter D2 of each of the end portions34. Further, the diameter D1 of the mid-portion 38 may be as large asabout 0.236 inches. Alternatively, the diameter D1 of the mid-portion 38may be as small as about 0.1 inches.

With reference to FIGS. 1-3 and 6, the insert bit 10 also includes anidentification band 50 coupled to the shank 22. As shown in FIG. 6, theband 50 is shaped as a ring and is made from elastomeric material havinga Scale A durometer of about 70 to about 90. Further, the insidediameter of the band 50 is less than the width of the Philips-style tip18, such that the band 50 must be stretched when inserted over the tip18 and onto the shank 22. Alternatively, the band 50 may be made from athin, heat-shrinkable material that is inserted over the tip 18 andshrunk with application of heat onto the shank 22. Further, the band 50may be configured with a non-cylindrical outer surface (e.g., ahexagonal outer surface).

With continued reference to FIG. 6, the shank 22 includes acircumferential groove 54 positioned between the concave portion 30 ofthe shank 22 and the drive portion 14 into which the band 50 is at leastpartially received. An inside diameter of the band 50 is less than orapproximately equal to a width or thickness of the shank 22 in thegroove 54 to yield an interference fit between the band 50 and the shank22. In other words, the band 50 is at least partially stretched from itsnaturally occurring or unstretched shape after it is assembled onto theshank 22. In addition to the interference fit between the band 50 andthe shank 22, an adhesive may be utilized to more permanently secure theband 50 to the shank 22. Alternatively, the circumferential groove 54 inthe shank 22 may be omitted, and the band 50 may be positioned over acylindrical portion of the shank 22 having an outer diameter greaterthan that of the concave portion 30 of the shank 22. Further, the band50 may be coupled to the insert bit 10 in a different location along thelength of the insert bit 10.

The identification band 50 may include any of a number of differentindicators 58 (FIG. 1) associated with a particular characteristic ofthe insert bit 10. For example, the indicator 58 may be configured as alogo or design printed upon, impregnated into, or molded into theidentification band 50 to indicate a manufacturer or brand of the insertbit 10. In addition, numbers, letters, or any combination thereof may beprinted upon, impregnated into, or molded into the identification band50 to indicate the particular size of the insert bit 10. Further, thecolor of the identification band 50 may serve as an indicator of aparticular characteristic of the insert bit 10 (e.g., a manufacturer orbrand identifier, sizing of the insert bit 10, etc.).

The insert bit 10 is manufactured from bar stock having a hexagonalcross-section. The tip 18 of the insert bit 10 is forged, and theconcave portion 30 of the shank 22 is machined to a particular length Land a particular radius R (FIG. 2) to facilitate elastic deformation ofthe concave portion 30 of the shank 22 when the insert bit 10 isutilized with an impact driver. In addition, a machining process may beemployed to create the circumferential groove 54 in the shank 22 inwhich the identification band 50 is positioned. Alternatively, any of anumber of different manufacturing processes may be employed to createthe insert bit 10. The insert bit 10 is also heat treated using atempering process to a hardness range between 52-60 HRC. Alternatively,the insert bit 10 may be heat treated to a hardness range between 54-59HRC. The same heat treating process is applied to the entire length ofthe insert bit 10, such that the resultant hardness of the insert bit 10is substantially uniform or non-varying, within a tolerance value, alongthe entire length of the insert bit 10. In other words, the hardness ofthe concave portion 30 of the shank 22 is similar to that of the tip 18and the drive portion 14 of the insert bit 10. Alternatively, a heattreating process may be employed to impart a varying hardness along thelength of the insert bit 10. Particularly, the shank 22 may be heattreated such that the hardness of the shank 22 varies along the length Lof the concave portion 30.

In operation of the insert bit 10, the concave portion 30 of the shank22 is configured to increase the impact resistance or the toughness ofthe insert bit 10, such that the tip 18 of the insert bit 10 is allowedto elastically deform or twist relative to the drive portion 14 aboutthe central axis 46 of the insert bit 10. Specifically, the polar momentof inertia of the shank 22 is decreased by incorporating the concaveportion 30, thereby reducing the amount of torsion required toelastically twist the shank 22, compared to a configuration of the shank22 having a cylindrical shape (i.e., without the reduced diametermid-portion 38).

FIGS. 7-11 illustrate another construction of an insert bit 10 a similarto the insert bit 10 of FIGS. 1-6, with like components or featureshaving like reference numerals including the letter “a.” However, theidentification band 50 is omitted in the insert bit 10 a of FIGS. 7-11(FIGS. 7-9). Rather, the concave portion 30 a of the shank 22 a extendsacross the entire length La of the shank 22 a. Also, the diameter D3 ofthe end portion 34 a adjacent the drive portion 14 a is larger than thediameter D2 of the end portion 34 a adjacent the tip 18 a. Specifically,the diameter D1 of the mid-portion 38 a is about 55% of the diameter D3of the end portion 34 a adjacent the drive portion 14 a. Alternatively,the diameter D1 may be about 45% to about 65% of the diameter D3. Therelative values between D1 and D2 for the insert bit 10 a are similar tothose for the insert bit 10. As a further alternative, the diameters D2,D3 may be substantially equal. The diameter D1 of the mid-portion 38 amay be as large as about 0.236 inches. Alternatively, the diameter D1 ofthe mid-portion 38 a may be as small as about 0.1 inches. The method ofmanufacturing the insert bit 10 a and the manner of operation of theinsert bit 10 a are substantially similar to that described above withrespect to the insert bit 10.

FIGS. 12-16 illustrate another construction of an insert bit 10 bsimilar to the insert bits 10, 10 a of FIGS. 1-6 and 7-11, respectively,with like components or features having like reference numeralsincluding the letter “b.” The identification band 50 is omitted in theinsert bit 10 b of FIGS. 12-16, and the groove of the drive portion(FIGS. 1-3 and FIGS. 7-9) is omitted in the insert bit 10 b of FIGS.12-16. Like the insert bit 10 a of FIGS. 7-11, the concave portion 30 bof the shank 22 b extends across the entire length Lb of the shank 22 b.The method of manufacturing the insert bit 10 b and the manner ofoperation of the insert bit 10 b are substantially similar to thatdescribed above with respect to the insert bit 10. However, the insertbit 10 b may not be utilized with a driver incorporating quick-releasestructure (e.g., a ball detent) because of the omission of the groove 26in the drive portion 14 b. The insert bit 10 b may, however, be utilizedwith a driver employing an interference fit to secure the insert bit 10b to the driver.

FIGS. 17 and 18 illustrate another construction of an insert bit 10 csimilar to the insert bit 10 of FIGS. 1-6, with like components orfeatures having like reference numerals with a letter “c.” The insertbit 10 c is configured with a shorter overall length Lt than that of theinsert bit 10. Specifically, the length of the drive portion 14 c isless than the length of the drive portion 14 of the insert bit 10, andthe length Lc of the concave portion 30 c is less than the length L ofthe concave portion 30 of the insert bit 10. Also, the groove 26 isomitted in the drive portion 14 c the insert bit 10 c, such that theinsert bit 10 c may not be utilized with a driver incorporating aquick-release structure (e.g., a ball detent). The insert bit 10 c may,however, be utilized with a driver employing an interference fit tosecure the insert bit 10 c to the driver.

Specifically, the insert bit 10 c of FIGS. 17 and 18 is configuredhaving an overall length Lt of about 1 inch. The curvature of theconcave portion 30 c is defined by a radius Rc of about 0.08 inches toabout 0.75 inches, and the length Lc of the concave portion 30 c of theshank 22 c is about 0.15 inches to about 0.35 inches. Therefore, a ratioof the radius Rc of the concave portion 30 c to the overall length Lt isabout 0.08 to about 0.75, and a ratio of the length Lc of the concaveportion 30 c of the shank 22 c to the overall length Lt is about 0.15 toabout 0.35. The diameter D1 of the mid-portion 38 c may be as large asabout 0.236 inches. Alternatively, the diameter D1 of the mid-portion 38c may be as small as about 0.1 inches. The method of manufacturing theinsert bit 10 c and the manner of operation of the insert bit 10 c aresubstantially similar to that described above with respect to the insertbit 10.

FIGS. 19-22 illustrate another construction of a tool bit or an insertbit 10 d including a hexagonal drive portion 14 d, a head or tip 18 dconfigured to engage a fastener, and a shank 22 d interconnecting thedrive portion 14 d and the tip 18 d. The hexagonal drive portion 14 d isintended to be engaged by any of a number of different tools, adapters,or components to receive torque from the tool, adapter, or component torotate the insert bit 10 d. For example, the insert bit 10 d may beutilized with a driver including a socket (not shown) having acorresponding hexagonal recess in which the hexagonal drive portion 14 dof the insert bit 10 d is received. The driver may also include a stemextending from the socket, which may be coupled to a handle for hand-useby an operator or to a chuck of a power tool (e.g., a drill) for powereduse by the operator. An interference fit between the hexagonal driveportion 14 d of the insert bit 10 d and the socket may be used toaxially secure the insert bit 10 d to the driver. Alternatively, aquick-release structure may be employed to axially secure the insert bit10 d to the driver. With reference to FIGS. 19 and 20, the drive portion14 d of the insert bit 10 d includes a groove 26 d into which thequick-release structure (e.g., a ball detent) may be positioned toaxially secure the insert bit 10 d to the driver. Alternatively, thegroove 26 d may be omitted from the drive portion 14 d of the insert bit10 d should an interference fit between the socket and the drive portion14 d be employed.

With continued reference to FIGS. 19 and 20, the tip 18 d of the insertbit 10 d is configured as a Philips-style tip 18 d (see also FIG. 21).Alternatively, the tip 18 d of the insert bit 10 d may be differentlyconfigured to engage different style fasteners. For example, the tip 18d of the insert bit 10 d may be configured as a straight blade(otherwise known as a “regular head”) to engage fasteners having acorresponding straight slot.

With reference to FIG. 20, a portion 30 d of the shank 22 d is concave,including opposite end portions 34 d and a reduced diameter mid-portion38 d. The concave portion 30 d of the shank 22 d includes an outerperipheral surface 42 d having a curvature in a plane including acentral axis 46 d (FIG. 19) of the insert bit 10 d (i.e., in a planeparallel to the plane of the page of FIG. 20). In a configuration of theinsert bit 10 d having an overall length Lt of about 3.5 inches, thecurvature is defined by a radius Rd of about 3 inches to about 50inches. More particularly, in a configuration of the insert bit 10 dhaving an overall length Lt of about 3.5 inches, the curvature isdefined by a radius Rd of about 5 inches to about 5.5 inches. In otherwords, in a configuration of the insert bit 10 d having an overalllength Lt of about 3.5 inches, a ratio of the radius Rd of the curvatureof the outer peripheral surface 42 d of the shank 22 d to the length Ltof the insert bit 10 d is between about 0.50:1 and about 14.3:1. Moreparticularly, in a configuration of the insert bit 10 d having anoverall length Lt of about 3.5 inches, a ratio of the radius Rd of thecurvature of the outer peripheral surface 42 d of the shank 22 d to thelength Lt of the insert bit 10 d is between about 1.25:1 and about1.75:1.

With continued reference to FIG. 20, in a configuration of the insertbit 10 d having an overall length Lt of about 3.5 inches, a ratio of thelength Ld of the concave portion 30 d of the shank 22 d to the overalllength Lt of the insert bit 10 d is about 0.2:1 to about 0.7:1. Moreparticularly, in a configuration of the insert bit 10 d having anoverall length Lt of about 3.5 inches, a ratio of the length Ld of theconcave portion 30 d of the shank 22 d to the overall length Lt of theinsert bit 10 d is about 0.3:1 to about 0.4:1. Considering the aboveratios of the radius Rd to the length Lt, a ratio of the radius Rd ofthe curvature of the outer peripheral surface 42 d of the shank 22 d tothe length Ld of the concave portion 30 d of the shank 22 d is betweenabout 0.7:1 and about 71.5:1. More particularly, in a configuration ofthe insert bit 10 d having an overall length Lt of about 3.5 inches, theratio of the radius Rd of the curvature of the outer peripheral surface42 d of the shank 22 d to the length Ld of the concave portion 30 d ofthe shank 22 d is between about 3.1:1 and about 5.8:1. Also, in aconfiguration of the insert bit 10 d having an overall length Lt ofabout 3.5 inches, a ratio of the diameter D1 of the mid-portion 38 d tothe diameter D2 of each of the end portions 34 d is about 0.7:1 to about0.8:1. The diameter D1 of the mid-portion 38 d may be as large as about0.236 inches. Alternatively, the diameter D1 of the mid-portion 38 d maybe as small as about 0.1 inches.

With reference to FIGS. 19 and 20, the drive portion 14 d and the tip 18d are coated with a layer or coating (e.g., manganese phosphate, etc.)to inhibit corrosion of the insert bit 10 d. In addition, the concaveportion 30 d of the shank 22 d is at least partially polished to asurface finish of at least about 2 microns to remove the coating fromthe shank 22 d. Alternatively, the concave portion 30 d of the shank 22d may be polished to a surface finish of about 1 micron to about 2microns to remove the coating from the shank 22 d. In the illustratedconstruction of the insert bit 10 d, the shank 22 d is polished alongthe entire length of the outer peripheral surface 42 d of the shank 22 dhaving the curvature Rd (i.e., the concave portion 30 d). Alternatively,less of the concave portion 30 d may be polished than what is shown inFIGS. 19 and 20.

The insert bit 10 d is manufactured from bar stock having a hexagonalcross-section. The tip 18 d of the insert bit 10 d is forged, and theconcave portion 30 d of the shank 22 d is machined to a particularlength Ld and a particular radius Rd (FIG. 20) to facilitate elasticdeformation of the concave portion 30 d of the shank 22 d when theinsert bit 10 d is utilized with an impact driver. Alternatively, any ofa number of different manufacturing processes may be employed to createthe insert bit 10 d. The insert bit 10 d is then heat treated using atempering process to a hardness range between about 52 HRC and about 60HRC. Alternatively, the insert bit 10 d may be heat treated to ahardness range between about 54 HRC and about 59 HRC The same heattreating process is applied to the entire length of the insert bit 10 d,such that the resultant hardness of the insert bit 10 d is substantiallyuniform or non-varying, within a tolerance value, along the entirelength of the insert bit 10 d. In other words, the hardness of theconcave portion 30 d of the shank 22 d is similar to that of the tip 18d and the drive portion 14 d of the insert bit 10 d. Alternatively, aheat treating process may be employed to impart a varying hardness alongthe length of the insert bit 10 d. Particularly, the shank 22 d may beheat treated such that the hardness of the shank 22 d varies along thelength Ld of the concave portion 30 d.

After the insert bit 10 d is heat treated, the corrosion-resistantcoating or layer (e.g., manganese phosphate, etc.) is applied to theentire insert bit 10 d to inhibit corrosion of the insert bit 10 d. Thecorrosion-resistant coating or layer may be applied in any of a numberof different ways (e.g., using a spraying or dipping process, plating,painting, steam tempering, etc.). After the insert bit 10 d is coated,the concave portion 30 d of the shank 22 d is polished to a surfacefinish of at least about 2 microns to remove the corrosion-resistantcoating or layer from the shank 22 d. In the illustrated construction ofthe insert bit 30 d, the concave portion 30 d is polished using anabrasive paper or sandpaper. Alternatively, the concave portion 30 d maybe polished in any of a number of different manners (e.g., byelectroplating, bead-blasting, using a vibration process with abrasives,etc.).

In operation of the insert bit 10 d, the concave portion 30 d of theshank 22 d is configured to increase the impact resistance or thetoughness of the insert bit 10 d, such that the tip 18 d of the insertbit 10 d is allowed to elastically deform or twist relative to the driveportion 14 d about the central axis 46 d of the insert bit 10 d.Specifically, the polar moment of inertia of the shank 22 d is decreasedby incorporating the concave portion 30 d, thereby reducing the amountof torsion required to elastically twist the shank 22 d, compared to aconfiguration of the shank 22 d having a cylindrical shape (i.e.,without the reduced diameter mid-portion 38 d). By polishing the concaveportion 30 d of the shank 22 d, the number and size of the microcracksin the concave portion 30 d of the shank 22 d are reduced, whichotherwise might result in undesirably high stress risers in the concaveportion 30 d that could ultimately shorten the useful life of the insertbit 10 d when used in an impact application.

FIGS. 23-26 illustrate another construction of a tool bit or an insertbit 10 e similar to the insert bit 10 d of FIGS. 19-22, with likecomponents or features having like reference numerals including theletter “e.” With reference to FIGS. 23-25, the tip 18 e of the insertbit 10 e is configured as a square tip 18 d configured to be receivedwithin a fastener having a square recess.

In a configuration of the insert bit 10 e having an overall length Lt ofabout 3.5 inches, the curvature of the concave portion 30 e is definedby a radius Re of about 3 inches to about 50 inches (FIG. 24). Moreparticularly, in a configuration of the insert bit 10 e having anoverall length Lt of about 3.5 inches, the curvature of the concaveportion 30 e is defined by a radius Re of about 5 inches to about 5.5inches. In other words, in a configuration of the insert bit 10 e havingan overall length Lt of about 3.5 inches, a ratio of the radius Re ofthe curvature of the outer peripheral surface 42 e of the shank 22 e tothe length Lt of the insert bit 10 e is between about 0.50:1 and about14.3:1. More particularly, in a configuration of the insert bit 10 ehaving an overall length Lt of about 3.5 inches, a ratio of the radiusRe of the curvature of the outer peripheral surface 42 e of the shank 22e to the length Lt of the insert bit 10 e is between about 1.25:1 andabout 1.75:1.

With continued reference to FIG. 24, in a configuration of the insertbit 10 e having an overall length Lt of about 3.5 inches, a ratio of thelength Le of the concave portion 30 e of the shank 22 e to the overalllength Lt of the insert bit 10 e is about 0.2:1 to about 0.7:1. Moreparticularly, in a configuration of the insert bit 10 e having anoverall length Lt of about 3.5 inches, a ratio of the length Le of theconcave portion 30 e of the shank 22 e to the overall length Lt of theinsert bit 10 e is about 0.3:1 to about 0.4:1. Considering the aboveratios of the radius Re to the length Lt, a ratio of the radius Re ofthe curvature of the outer peripheral surface 42 e of the shank 22 e tothe length Le of the concave portion 30 e of the shank 22 e is betweenabout 0.7:1 and about 71.5:1. More particularly, in a configuration ofthe insert bit 10 e having an overall length Lt of about 3.5 inches, theratio of the radius Re of the curvature of the outer peripheral surface42 e of the shank 22 e to the length Le of the concave portion 30 e ofthe shank 22 e is between about 3.1:1 and about 5.8:1. Also, in aconfiguration of the insert bit 10 e having an overall length Lt ofabout 3.5 inches, a ratio of the diameter D1 of the mid-portion 38 e tothe diameter D2 of each of the end portions 34 e is about 0.7:1 to about0.8:1. The diameter D1 of the mid-portion 38 e may be as large as about0.236 inches. Alternatively, the diameter D1 of the mid-portion 38 e maybe as small as about 0.1 inches.

Like the insert bit 10 d, the drive portion 14 e and the tip 18 e of theinsert bit 10 e are coated with a layer or coating (e.g., manganesephosphate, etc.) to inhibit corrosion of the insert bit 10 e. Inaddition, the concave portion 30 e of the shank 22 e is at leastpartially polished to a surface finish of at least about 2 microns toremove the coating from the shank 22 e. Alternatively, the concaveportion 30 e of the shank 22 e may be polished to a surface finish ofabout 1 micron to about 2 microns to remove the coating from the shank22 e. In the illustrated construction of the insert bit 10 e, the shank22 e is polished along the entire length of the outer peripheral surface42 e of the shank 22 e having the curvature Re (i.e., the concaveportion 30 e). The method of manufacturing the insert bit 10 e and themanner of operation of the insert bit 10 e are substantially similar tothat described above with respect to the insert bit 10 d.

FIGS. 27-30 illustrate another construction of a tool bit or an insertbit 10 f similar to the insert bit 10 d of FIGS. 19-22, with likecomponents or features having like reference numerals including theletter “f.” With reference to FIGS. 27-29, the tip 18 e of the insertbit 10 e is configured as a Philips-style tip 18 f. Alternatively, thetip 18 f may be differently configured to engage different stylefasteners. For example, the tip 18 f may be configured as a straightblade (otherwise known as a “regular head”) to engage fasteners having acorresponding straight slot.

In a configuration of the insert bit 10 f having an overall length Lt ofabout 2 inches, the curvature of the concave portion 30 f is defined bya radius Rf of about 1 inch to about 2 inches (FIG. 28). Moreparticularly, in a configuration of the insert bit 10 f having anoverall length Lt of about 2 inches, the curvature of the concaveportion 30 f is defined by a radius Rf of about 1.5 inches. In otherwords, in a configuration of the insert bit 10 f having an overalllength Lt of about 2 inches, a ratio of the radius Rf of the curvatureof the outer peripheral surface 42 f of the shank 22 f to the length Ltof the insert bit 10 f is between about 0.50:1 and about 2:1. Moreparticularly, in a configuration of the insert bit 10 f having anoverall length Lt of about 2 inches, a ratio of the radius Rf of thecurvature of the outer peripheral surface 42 f of the shank 22 f to thelength Lt of the insert bit 10 f is between about 0.5:1 and about 1:1.

With continued reference to FIG. 28, in a configuration of the insertbit 10 f having an overall length Lt of about 2 inches, a ratio of thelength Lf of the concave portion 30 f of the shank 22 f to the overalllength Lt of the insert bit 10 f is about 0.2:1 to about 0.6:1. Moreparticularly, in a configuration of the insert bit 10 f having anoverall length Lt of about 2 inches, a ratio of the length Lf of theconcave portion 30 f of the shank 22 f to the overall length Lt of theinsert bit 10 f is about 0.2 inches to about 0.3 inches. Considering theabove ratios of the radius Rf to the length Lt, a ratio of the radius Rfof the curvature of the outer peripheral surface 42 f of the shank 22 fto the length Lf of the concave portion 30 f of the shank 22 f isbetween about 0.8:1 and about 10:1. More particularly, in aconfiguration of the insert bit 10 f having an overall length Lt ofabout 2 inches, the ratio of the radius Rf of the curvature of the outerperipheral surface 42 f of the shank 22 f to the length Lf of theconcave portion 30 f of the shank 22 f is between about 1.7:1 and about5:1.

With continued reference to FIG. 28, in a configuration of the insertbit 10 f having an overall length Lt of about 2 inches, a ratio of thediameter D1 of the mid-portion 38 f to the diameters D2, D3 of the endportions 34 f is about 0.7:1 to about 0.9:1. Similar to the insert bit10 a, the diameter D3 of the end portion 34 f adjacent the drive portion14 f is larger than the diameter D2 of the end portion 34 f adjacent thetip 18 f. A ratio of the diameter D1 of the mid-portion 38 f to thediameter D3 of the end portion 34 f adjacent the drive portion 14 f isabout 0.75:1, while a ratio of the diameter D1 of the mid-portion 38 fto the diameter D2 of the end portion 34 f adjacent the tip 18 f isabout 0.83:1. Alternatively, the diameters D2, D3 may be substantiallyequal. The diameter D1 of the mid-portion 38 f may be as large as about0.236 inches. Alternatively, the diameter D1 of the mid-portion 38 f maybe as small as about 0.1 inches.

Like the insert bit 10 d, the drive portion 14 f and the tip 18 f of theinsert bit 10 f are coated with a layer or coating (e.g., manganesephosphate, etc.) to inhibit corrosion of the insert bit 10 f. Inaddition, the concave portion 30 f of the shank 22 f is at leastpartially polished to a surface finish of at least about 2 microns toremove the coating from the shank 22 f. Alternatively, the concaveportion 30 f of the shank 22 f may be polished to a surface finish ofabout 1 micron to about 2 microns to remove the coating from the shank22 f. In the illustrated construction of the insert bit 10 f, the shank22 f is polished along the entire length of the outer peripheral surface42 f of the shank 22 f having the curvature Rf (i.e., the concaveportion 30 f). The method of manufacturing the insert bit 10 f and themanner of operation of the insert bit 10 f are substantially similar tothat described above with respect to the insert bit 10 d.

FIGS. 31-34 illustrate another construction of a tool bit or an insertbit 10 g similar to the insert bit 10 f of FIGS. 27-30, with likecomponents or features having like reference numerals including theletter “g.” With reference to FIGS. 31-33, the tip 18 g of the insertbit 10 g is configured as a square tip 18 g configured to be receivedwithin a fastener having a square recess.

In a configuration of the insert bit 10 g having an overall length Lt ofabout 2 inches, the curvature of the concave portion 30 g is defined bya radius Rg of about 1 inch to about 2 inches (FIG. 32). Moreparticularly, in a configuration of the insert bit 10 g having anoverall length Lt of about 2 inches, the curvature of the concaveportion 30 g is defined by a radius Rg of about 1.5 inches. In otherwords, in a configuration of the insert bit 10 g having an overalllength Lt of about 2 inches, a ratio of the radius Rg of the curvatureof the outer peripheral surface 42 g of the shank 22 g to the length Ltof the insert bit 10 g is between about 0.50:1 and about 2:1. Moreparticularly, in a configuration of the insert bit 10 g having anoverall length Lt of about 2 inches, a ratio of the radius Rg of thecurvature of the outer peripheral surface 42 g of the shank 22 g to thelength Lg of the insert bit 10 g is between about 0.5:1 and about 1:1.

With continued reference to FIG. 32, in a configuration of the insertbit 10 g having an overall length Lt of about 2 inches, a ratio of thelength Lg of the concave portion 30 g of the shank 22 g to the overalllength Lt of the insert bit 10 g is about 0.2:1 to about 0.6:1. Moreparticularly, in a configuration of the insert bit 10 g having anoverall length Lt of about 2 inches, a ratio of the length Lg of theconcave portion 30 g of the shank 22 g to the overall length Lt of theinsert bit 10 g is about 0.2:1 to about 0.3:1. Considering the aboveratios of the radius Rg to the length Lt, a ratio of the radius Rg ofthe curvature of the outer peripheral surface 42 g of the shank 22 g tothe length Lg of the concave portion 30 g of the shank 22 g is betweenabout 0.8:1 and about 10:1. More particularly, in a configuration of theinsert bit 10 g having an overall length Lt of about 2 inches, the ratioof the radius Rg of the curvature of the outer peripheral surface 42 gof the shank 22 g to the length Lg of the concave portion 30 g of theshank 22 g is between about 1.7:1 and about 5:1.

With continued reference to FIG. 32, in a configuration of the insertbit 10 g having an overall length Lt of about 2 inches, a ratio of thediameter D1 of the mid-portion 38 g to the diameters D2, D3 of the endportions 34 g is about 0.7:1 to about 0.9:1. Similar to the insert bit10 f, the diameter D3 of the end portion 34 g adjacent the drive portion14 g is larger than the diameter D2 of the end portion 34 g adjacent thetip 18 g. Specifically, a ratio of the diameter D1 of the mid-portion 38g to the diameter D3 of the end portion 34 g adjacent the drive portion14 g is about 0.74:1, while a ratio of the diameter D1 of themid-portion 38 g to the diameter D2 of the end portion 34 g adjacent thetip 18 g is about 0.85:1. Alternatively, the diameters D2, D3 may besubstantially equal. The diameter D1 of the mid-portion 38 g may be aslarge as about 0.236 inches. Alternatively, the diameter D1 of themid-portion 38 g may be as small as about 0.1 inches.

Like the insert bit 10 f, the drive portion 14 g and the tip 18 g of theinsert bit 10 g are coated with a layer or coating (e.g., manganesephosphate, etc.) to inhibit corrosion of the insert bit 10 g. Inaddition, the concave portion 30 g of the shank 22 g is at leastpartially polished to a surface finish of at least about 2 microns toremove the coating from the shank 22 g. Alternatively, the concaveportion 30 g of the shank 22 g may be polished to a surface finish ofabout 1 micron to about 2 microns to remove the coating from the shank22 g. In the illustrated construction of the insert bit 10 g, the shank22 g is polished along the entire length of the outer peripheral surface42 g of the shank 22 g having the curvature Rg (i.e., the concaveportion 30 g). The method of manufacturing the insert bit 10 g and themanner of operation of the insert bit 10 g are substantially similar tothat described above with respect to the insert bit 10 d.

FIGS. 35-38 illustrate another construction of a tool bit or an insertbit 10 h similar to the insert bit 10 f of FIGS. 27-30, with likecomponents or features having like reference numerals including theletter “h.” With reference to FIGS. 35-37, the tip 18 h of the insertbit 10 h is configured as a TORX screw tip 18 g.

In a configuration of the insert bit 10 h having an overall length Lt ofabout 2 inches, the curvature of the concave portion 30 h is defined bya radius Rh of about 1 inch to about 2 inches (FIG. 36). Moreparticularly, in a configuration of the insert bit 10 h having anoverall length Lt of about 2 inches, the curvature of the concaveportion 30 h is defined by a radius Rh of about 1.5 inches. In otherwords, in a configuration of the insert bit 10 h having an overalllength Lt of about 2 inches, a ratio of the radius Rh of the curvatureof the outer peripheral surface 42 h of the shank 22 h to the length Ltof the insert bit 10 h is between about 0.50:1 and about 2:1. Moreparticularly, in a configuration of the insert bit 10 h having anoverall length Lt of about 2 inches, a ratio of the radius Rh of thecurvature of the outer peripheral surface 42 h of the shank 22 h to thelength Lh of the insert bit 10 h is between about 0.5:1 and about 1:1.

With continued reference to FIG. 36, in a configuration of the insertbit 10 h having an overall length Lt of about 2 inches, a ratio of thelength Lh of the concave portion 30 h of the shank 22 h to the overalllength Lt of the insert bit 10 h is about 0.2:1 to about 0.6:1. Moreparticularly, in a configuration of the insert bit 10 h having anoverall length Lt of about 2 inches, a ratio of the length Lh of theconcave portion 30 h of the shank 22 h to the overall length Lt of theinsert bit 10 h is about 0.2:1 to about 0.3:1. Considering the aboveratios of the radius Rh to the length Lt, a ratio of the radius Rh ofthe curvature of the outer peripheral surface 42 h of the shank 22 h tothe length Lh of the concave portion 30 h of the shank 22 h is betweenabout 0.8:1 and about 10:1. More particularly, in a configuration of theinsert bit 10 h having an overall length Lt of about 2 inches, the ratioof the radius Rh of the curvature of the outer peripheral surface 42 hof the shank 22 h to the length Lh of the concave portion 30 h of theshank 22 h is between about 1.7:1 and about 5:1.

With continued reference to FIG. 36, in a configuration of the insertbit 10 h having an overall length Lt of about 2 inches, a ratio of thediameter D1 of the mid-portion 38 h to the diameters D2, D3 of the endportions 34 h is about 0.7:1 to about 0.95:1. Similar to the insert bit10 f, the diameter D3 of the end portion 34 h adjacent the drive portion14 h is larger than the diameter D2 of the end portion 34 h adjacent thetip 18 h. Specifically, a ratio of the diameter D1 of the mid-portion 38h to the diameter D3 of the end portion 34 h adjacent the drive portion14 h is about 0.74:1, while a ratio of the diameter D1 of themid-portion 38 h to the diameter D2 of the end portion 34 h adjacent thetip 18 h is about 0.95:1. Alternatively, the diameters D2, D3 may besubstantially equal. The diameter D1 of the mid-portion 38 h may be aslarge as about 0.236 inches. Alternatively, the diameter D1 of themid-portion 38 h may be as small as about 0.1 inches.

Like the insert bit 10 f, the drive portion 14 h and the tip 18 h of theinsert bit 10 h are coated with a layer or coating (e.g., manganesephosphate, etc.) to inhibit corrosion of the insert bit 10 h. Inaddition, the concave portion 30 h of the shank 22 h is at leastpartially polished to a surface finish of at least about 2 microns toremove the coating from the shank 22 h. Alternatively, the concaveportion 30 h of the shank 22 h may be polished to a surface finish ofabout 1 micron to about 2 microns to remove the coating from the shank22 h. In the illustrated construction of the insert bit 10 h, the shank22 h is polished along the entire length of the outer peripheral surface42 h of the shank 22 h having the curvature Rh (i.e., the concaveportion 30 h). The method of manufacturing the insert bit 10 h and themanner of operation of the insert bit 10 h are substantially similar tothat described above with respect to the insert bit 10 d.

FIGS. 39-42 illustrate another construction of a tool bit or an insertbit 10 i including a hexagonal drive portion 14 i, a head or tip 18 iconfigured to engage a fastener, and a shank 22 i interconnecting thedrive portion 14 i and the tip 18 i. The insert bit 10 i may be utilizedwith a driver including a socket (not shown) having a correspondinghexagonal recess in which the hexagonal drive portion 14 i of the insertbit 10 i is received. The driver may also include a stem extending fromthe socket, which may be coupled to a handle for hand-use by anoperator, or to a chuck of a power tool (e.g., a drill) for powered useby the operator. An interference fit between the hexagonal drive portion14 i of the insert bit 10 i and the socket may be used to axially securethe insert bit 10 i to the driver.

With reference to FIGS. 39-41, the tip 18 i is configured as aPhilips-style tip 18 i. Alternatively, the tip 18 i may be differentlyconfigured to engage different style fasteners. For example, the tip 18i may be configured as a straight blade (otherwise known as a “regularhead”) to engage fasteners having a corresponding straight slot.

With reference to FIGS. 39 and 40, the drive portion 14 i and the tip 18i are coated with a layer or coating (e.g., manganese phosphate, etc.)to inhibit corrosion of the insert bit 10 i. In addition, at least aportion of the shank 22 i is polished to a surface finish of at leastabout 2 microns to remove the coating from the shank 22 i.Alternatively, the shank 22 i may be polished to a surface finish ofabout 1 micron to about 2 microns to remove the coating from the shank22 i.

The insert bit 10 i is manufactured from bar stock having a hexagonalcross-section. The tip 18 i of the insert bit 10 i is forged, and theshank 22 i is machined to a substantially cylindrical shape tofacilitate elastic deformation of the shank 22 i when the insert bit 10i is utilized with an impact driver. Alternatively, any of a number ofdifferent manufacturing processes may be employed to create the insertbit 10 i. The insert bit 10 i is then heat treated using a temperingprocess to a hardness range between about 52 HRC and about 60 HRC.Alternatively, the insert bit 10 i may be heat treated to a hardnessrange between about 54 HRC and about 59 HRC. The same heat treatingprocess is applied to the entire length of the insert bit 10 i, suchthat the resultant hardness of the insert bit 10 i is substantiallyuniform or non-varying, within a tolerance value, along the entirelength of the insert bit 10 i. Alternatively, a heat treating processmay be employed to impart a varying hardness along the length of theinsert bit 10 i.

After the insert bit 10 i is heat treated, the corrosion-resistantcoating or layer (e.g., manganese phosphate, etc.) is applied to theentire insert bit 10 i to inhibit corrosion of the insert bit 10 i. Thecorrosion-resistant coating or layer may be applied in any of a numberof different ways (e.g., using a spraying or dipping process, plating,painting, steam tempering, etc.). After the insert bit 10 i is coated, aportion of the shank 22 i is polished to a surface finish of at leastabout 2 microns to remove the corrosion-resistant coating or layer fromthe shank 22 i. In the illustrated construction of the insert bit 10 i,the shank 22 i is polished using an abrasive paper or sandpaper.Alternatively, the shank 22 i may be polished in any of a number ofdifferent manners (e.g., by electroplating, bead-blasting, using avibration process with abrasives, etc.).

In operation of the insert bit 10 i, the shank 22 i is configured toincrease the impact resistance or the toughness of the insert bit 10 i,such that the tip 18 i of the insert bit 10 i is allowed to elasticallydeform or twist relative to the drive portion 14 i about the centralaxis 46 i of the insert bit 10 i. Specifically, the polar moment ofinertia of the shank 22 i is less than that of the drive portion 14 i,thereby reducing the amount of torsion required to elastically twist theshank 22 i. By polishing the shank 22 i, the number and size of themicrocracks in the shank 22 i are reduced, which otherwise might resultin undesirably high stress risers in the shank 22 i that couldultimately shorten the useful life of the insert bit 10 i when used inan impact application.

FIGS. 43-46 illustrate another construction of a tool bit or an insertbit 10 j, with like components or features having like referencenumerals including the letter “j.” With reference to FIGS. 43-45, thetip 18 j of the insert bit 10 j is configured as a square tip 18 jconfigured to be received within a fastener having a square recess.

With reference to FIG. 44, the shank 22 j includes a tapered cylindricalshape defining an included angle A of about 4.5 degrees. Alternatively,the shank 22 j may include a tapered cylindrical shape defining an angleA more or less than about 4.5 degrees. As a further alternative, theshank 22 j may include a substantially cylindrical shape similar to theshank 22 i of the insert bit 10 i.

Also, like the insert bit 10 i, the drive portion 14 j and the tip 18 jof the insert bit 10 j are coated with a layer or coating (e.g.,manganese phosphate, etc.) to inhibit corrosion of the insert bit 10 j.In addition, at least a portion of the shank 22 j is polished to asurface finish of at least about 2 microns to remove the coating fromthe shank 22 j. Alternatively, the shank 22 j may be polished to asurface finish of about 1 micron to about 2 microns to remove thecoating from the shank 22 j. The method of manufacturing the insert bit10 j and the manner of operation of the insert bit 10 j aresubstantially similar to that described above with respect to the insertbit 10 i.

FIGS. 47-50 illustrate another construction of a tool bit or an insertbit 10 k that is similar to the insert bit 10 j of FIGS. 43-46, withlike components or features having like reference numerals including theletter “k.” With reference to FIGS. 47-49, the tip 18 k of the insertbit 10 k is configured as a TORX screw tip 18 k.

With reference to FIG. 48, the shank 2 kj includes a tapered cylindricalshape defining an included angle A of about 4.5 degrees. Alternatively,the shank 22 k may include a tapered cylindrical shape defining an angleA more or less than about 4.5 degrees. As a further alternative, theshank 22 k may include a substantially cylindrical shape similar to theshank 22 i of the insert bit 10 i.

Also, like the insert bits 10 i, 10 j, the drive portion 14 k and thetip 18 k of the insert bit 10 k are coated with a layer or coating(e.g., manganese phosphate, etc.) to inhibit corrosion of the insert bit10 k. In addition, at least a portion of the shank 22 k is polished to asurface finish of at least about 2 microns to remove the coating fromthe shank 22 k. Alternatively, the shank 22 k may be polished to asurface finish of about 1 micron to about 2 microns to remove thecoating from the shank 22 k. The method of manufacturing the insert bit10 k and the manner of operation of the insert bit 10 k aresubstantially similar to that described above with respect to the insertbit 10 i.

Various features of the invention are set forth in the following claims.

What is claimed is:
 1. A tool bit comprising: a hexagonal drive portion;a working end; and a shank interconnecting the drive portion and theworking end, wherein the shank includes an outer peripheral surfacehaving a curvature in a plane including a central axis of the tool bit,wherein the outer peripheral surface having the curvature includes alength in the direction of the central axis, and wherein a ratio of thelength of the outer peripheral surface having the curvature to thelength of the tool bit is between about 0.2:1 and about 0.7:1.
 2. Thetool bit of claim 1, wherein the ratio of the length of the outerperipheral surface to the length of the tool bit is between about 0.3:1and about 0.4:1.
 3. The tool bit of claim 1, wherein the ratio of thelength of the outer peripheral surface to the length of the tool bit isbetween about 0.2:1 and about 0.3:1.
 4. The tool bit of claim 1, whereinthe curvature is defined by a radius, and wherein a ratio of the radiusof the curvature of the outer peripheral surface of the shank to thelength of the tool bit is between about 0.50:1 and about 14.3:1.
 5. Thetool bit of claim 4, wherein the ratio of the radius of the curvature ofthe outer peripheral surface of the shank to the length of the tool bitis between about 1.25:1 and about 1.75:1.
 6. The tool bit of claim 4,wherein the ratio of the radius of the curvature of the outer peripheralsurface of the shank to the length of the tool bit is between about0.50:1 and about 1:1.
 7. The tool bit of claim 1, wherein the outerperipheral surface having the curvature defines a maximum diameter ofthe shank and a minimum diameter of the shank, and wherein a ratio ofthe minimum diameter to the maximum diameter is between about 0.7:1 andabout 0.95:1.
 8. The tool bit of claim 1, wherein the curvature isdefined by a radius between about 3 inches and about 50 inches.
 9. Thetool bit of claim 1, wherein the curvature is defined by a radiusbetween about 1 inch and about 2 inches.
 10. The tool bit of claim 1,wherein at least a portion of the shank is polished to a surface finishof at least about 2 microns.
 11. The tool bit of claim 10, wherein theouter peripheral surface having the curvature includes a length, andwherein the shank is polished to a surface finish of at least about 2microns along the entire length of the outer peripheral surface havingthe curvature.
 12. The tool bit of claim 1, wherein the hexagonal driveportion and the working end each include a corrosion-resistant coating.13. The tool bit of claim 1, wherein the tool bit includes a hardnessbetween about 52 HRC and about 60 HRC.